I think it was about 2 weeks when I saw the new account number listed on my CR's and when I pulled up my account on the BOA website. It took 4 weeks to the day for the new card to actually arrive. I was told to keep using the old one until I got the new one.
Mine took a long time as well. As the PP suggested it takes a few weeks or a little less for the website to show the new card and mine appeared in stages, where both cards were showing at one time and then I got the new card in the mail a week or two later I think (if I recall correctly...I posted about it if you want to search for it). Then the old card disappeared and only the new remained. Seemless transition on credit reports so that was nice.